Summary
Caddy: mTLS client authentication silently fails open when CA certificate file is missing or malformed
Impact
Any deployment using trusted_ca_cert_file or trusted_ca_certs_pem_files for mTLS will silently degrade to accepting any system-trusted client certificate if the CA file becomes unavailable. This can happen due to a typo in the path, file rotation, corruption, or permission changes. The server gives no indication that mTLS is misconfigured.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-27586? CVE-2026-27586 is a high-severity security vulnerability in github.com/caddyserver/caddy/v2 (go), affecting versions < 2.11.1. It is fixed in 2.11.1.
- Which versions of github.com/caddyserver/caddy/v2 are affected by CVE-2026-27586? github.com/caddyserver/caddy/v2 (go) versions < 2.11.1 is affected.
- Is there a fix for CVE-2026-27586? Yes. CVE-2026-27586 is fixed in 2.11.1. Upgrade to this version or later.
- Is CVE-2026-27586 exploitable, and should I be worried? Whether CVE-2026-27586 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-27586 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-27586? Upgrade
github.com/caddyserver/caddy/v2to 2.11.1 or later.